There are two signed Silmarillion's on Ebay at the moment, the other one is clearly genuine and signed by Christopher Tolkien and Alan Lee, the signature is completely different so I am very suspicious about this one.

I can assure you that the Silmarillion on Ebay (below) is genuine, signed by both C.Tolkien and Ted Nasmith. I know this because I got the book directly from the publishing company HarperCollins while working there a few years ago.

I worked for the entertainment section which was responsible for all official publishing of Tolkien books and was also responsible for the official website: www.tolkien.co.uk (which sadly has become out of date since leaving! )